Failure analysis of oxygen hose of the lance equipment in LD shop of Tata steel

The hose of the oxygen lancing equipment in LD shop # 2 has failed at the weld-bellows interface by reverse bending fatigue. The bending stresses were resulted due to inclined fitting of the hose at the fixed flange end. No metallurgical abnormalities or weld defects or mechanical damages were responsible for the fatigue crack initiation. It is recommended that if inclined fitment of the hose is not a process requirement, the original design be restored to realize the expected life of the component. On the other hand, if inclined fitment cannot be avoided, additional support may be provided for the hose at the fixed flange end to avoid reverse bending at the weld-bellows interface. A detailed analysis of the failure is presented in this report.